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P300H P300 Series Modem Installation and Operating Handbook Page 156
The AUPC can also be set in self monitor mode (Self Mon). This is used when a single Tx carrier is used
to broadcast information to multiple Rx sites. Provided the local modem Rx path is locked to this broadcast
carrier then the local Eb/No indicates any atmospheric changes on the local end satellite uplink and down
link. In this mode the AUPC controls the local Tx power by directly monitoring the local Eb/No. This is an
imperfect system as it changes the local Tx power to compensate for local atmospheric changes which
affect the local uplink and downlink, it cannot however compensate for distant atmospheric changes
affecting the multiple distant downlinks. Self Mon mode requires no ESC channel as the AUPC software
can directly read the local Eb/No as well as control the local Tx power.
If AUPC is active in normal (Maint' Eb/No) or self monitor (Self Mon) modes then the status of the AUPC
can be displayed (Monitor, AUPC), also the AUPC delta power can be recorded regularly in the traffic log
using the Autolog feature (Change, Log, Autolog). The AUPC delta power can also be output on the
uncommitted analog DAC output if the Monitor / AGC option is fitted (again see “uncommitted analog DAC
output”, value = 5 in Appendix E starting on page 201)
The speed of reaction of the AUPC depends primarily on two factors: The user specified slew rate
(specifically to limit the rate of change of Tx power when a power adjustment is deemed necessary), and
the ESC channel Baud rate (which affects how regularly the distant Eb/No is read by the local modem in
order to determine if any adjustment is necessary).
The AUPC will use a different proportion of the available ESC bandwidth depending on the ESC interface
selected.
If the ESC interface is set to Link to M&C (Link-L or Link-R) then it assumes the ESC channel is also
being used for network M&C (as this is the setting used to provide the connectivity for distant end M&C).
In this case the AUPC will use up to 33% of the ESC channel bandwidth in order to achieve an Eb/No
reporting rate of once per second. If the ESC Baud rate is such (ie so high) that the AUPC can achieve
this update rate using less than 33% of the ESC channel bandwidth, then it uses only the proportion
of bandwidth required for a 1Hz update rate. The 33% bandwidth is used by interleaving the requests